Dynamic positioning connection

ABSTRACT

A method of providing for the dynamic positioning of a vessel comprising providing a dynamically positioned service boat, linking the service boat to the vessel by a rigid link with a first connection between the link and the vessel, a second connection between the link and the service boat, the combination of connections having 3 degrees of rotational freedom, said supply boat having one degree of axial freedom relative to said vessel, and using the power of the service boat to dynamically position said vessel in a desired location.

BACKGROUND OF THE INVENTION

In shallow waters, pipelay is primarily done by an “S-Lay” method, whichmeans that the welding is done along the deck of a flat barge and thenthe pipe bends down to the ocean floor in a sort of “S” curve. The pipebends down on a radiused stinger and then naturally curves back tohorizontal as it reaches the ocean floor. In deeper water, the forces onthe stinger and the size of the required stinger make it more favorableto weld the pipe together in a near vertical position and have a singlebend at the ocean floor. The forms a “J” in the pipe and gives it thename of the “J-Lay” method.

Offshore deepwater pipeline laying systems are characteristicallylimited to high cost specialty vessels due the combination of loads andpositioning required to accomplish the pipelaying. J-Lay pipelay systemsare characteristically complicated and require special connections tothe vessel. This makes a costly specialty custom vessel an appropriateinvestment. As the custom vessel is an appropriate investment,investment in onboard dynamic positioning also becomes an appropriateinvestment.

Dynamic positioning is using the propellers to actively hold the vesselin position, in contrast to passively holding the vessel in positionwith anchors and anchor lines.

A pipelay system such as the Flex J-lay Tower described in U.S. Pat. No.6,776,560 provides the unique ability to be simply mounted on a flat andeconomical barge. Such a barge or vessel would typically not havedynamic positioning available. The barge or vessel could then bepositioned along the pipeline route by one or more service boats whichcan provide the dynamic positioning capability. The service boats wouldbe connected to the barge or vessel by the connections of thisinvention.

Such service boats have previously been connected to vessels of thistype by a rope, which provides only an axial tension. If the serviceboat wants to provide a force on the vessel in any direction other thanstraight along the rope, the service boat must move radially around theconnection point on the vessel to another position. The service boatcould then pull in that direction only.

An appropriate mechanical connection would have the ability for theservice boat to push or pull the vessel. When the service boat has ahorizontal bow thruster, it can provide a sideways force on theconnection, and therefore on the vessel. By combinations of axial thrustand sideways bow thrusters, the service boat can impart a force on thevessel in any horizontal direction.

A complication to a mechanical connection between the vessel and theservice boat is that the larger vessel and the smaller supply boat willcharacteristically have different periods of vertical motion. As one isgoing up, the other will be going down at some times during operations.

BRIEF SUMMARY OF THE INVENTION

The object of this invention is to provide a system for improveddynamically positioning a vessel by mechanically connecting one or moredynamically positioned service boats to the vessel.

A second object of the present invention is to provide 3 degrees ofrotational freedom on the mechanical connection between the vessel andthe one or more service boats.

A third object of the present invention is to provide one degree ofaxial freedom for normal operations.

Another object of the present invention is to provide a second degree ofmechanical freedom when desired.

Another object of the present invention is to allow the service boat toexert a sideways force on the vessel.

Another object of this invention is to allow the service boat to exert apush or pull on the vessel in any direction

BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a view of a j-lay system on a barge and of a supporting pipebarge, each having service boats connected by connections of thisinvention for dynamic positioning.

FIG. 2 is a view of a portion of the pipelay barge and a service boatwith the connection of this invention between.

FIG. 3 is an enlarged view of the joint between the central connectionmember and the pipelay barge.

FIG. 4 is an enlarged view of the joint between the central connectionmember and the service boat with dynamic positioning.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows a pipelay vessel 1 with a j-lay tower 2 mounted on the deck4. A pipe supporting mechanism 6 is shown with a portion of the pipeline8 suspended in the ocean water. Service boats 10 and 12 are attached tothe pipelay vessel 1 by links 14 and 16 respectively.

Side thrusters 18 are provided near the bow of the service boats 10 and12 which enable the service boats to provide a lateral force on links 14and 16. Various combinations of lateral and axial forces from theservice boat to the vessel allow the service boat to impart forces inany direction to the vessel.

An additional barge 20 is shown in a position to re-supply the pipelayvessel 1 with pipe or other supplies. A third service boat 22 is shownattached by link 24.

Referring now to FIG. 2, link 14 is shown between vessel 1 and serviceboat 10. Pivoting joint 30 is shown engaging funnel 32 which is mountedto vessel 1 at 34. The mounting can be prepared and permanently affixedto the vessel 1, can be removeably attached, or can be magneticallyattached.

Pivoting joint 40 is shown engaging funnel 42 which is mounted toservice boat 10 at 44. Portion 46 of the mounting can be prepared andpermanently affixed to the vessel 10 and portion 48 can be bolted toportion 46.

Link 14 has a main axial member 50 and a structure 52. Cables or chains54 and 56 connect between structure 52 and service boat 10 to restrictrotational movement in the plane of the surface of the ocean,restricting the two vessels to a single degree of axial freedom relativeto each other. When an extra degree of axial freedom is desired, tensioncan be released on cables or chains 54 and 56. Buoyancy material 58 isshown generally within the structure 52 to make the structure 52positively buoyant.

Cables or chains can be installed on the opposite end of the link andattached directly to the vessel to restrict the degree of motion on theopposite end of the link.

Referring now to FIG. 3, pivoting joint 30 is shown in greater detail.Central member 60 is pivoted horizontally relative to main axial member50 about a vertical pin generally located at 62 (not shown). Motor 63can be powered to rotate central member 60 about the vertical pinlocated at 62. Stab 64 is pivoted vertically relative to central member60 about a horizontal pin generally located at 66 (not shown). Stab 64lockingly engages funnel 32 to connect to vessel 1 and can rotate aboutthe centerline of the stab. Cylinder 68 can be used to position the stab64 when the stabbing connection is made. Vertical pin at 62, horizontalpin at 66, and stab 64 provide 3 degrees of angular freedom.

Referring now to FIG. 4, pivoting joint 40 is shown in greater detail.Central member 70 is pivoted horizontally relative to main axial member50 about a vertical pin generally located at 72 (not shown). Motor 73can be powered to rotate central member 70 about the vertical pinlocated at 72. Stab 74 is pivoted vertically relative to central member70 about a horizontal pin generally located at 76 (not shown). Stab 74lockingly engages funnel 42 to connect to service boat 10 and can rotateabout the centerline of the stab. Cylinder 78 can be used to positionthe stab 74 when the stabbing connection is made. Horizontal pin at 66vertical pin at 76, and stab 74 provide decrees of angular freedom.

The particular embodiments disclosed above are illustrative only, as theinvention may be modified and practiced in different but equivalentmanners apparent to those skilled in the art having the benefit of theteachings herein. Furthermore, no limitations are intended to thedetails of construction or design herein shown, other than as describedin the claims below. It is therefore evident that the particularembodiments disclosed above may be altered or modified and all suchvariations are considered within the scope and spirit of the invention.Accordingly, the protection sought herein is as set forth in the claimsbelow.

1. A method of providing for the dynamic positioning of a vesselcomprising providing a dynamically positioned service boat, providing alink, providing a first connection between said link and said vessel,providing a second connection between said link and said service boat,providing three degrees of rotational freedom by the combination of saidfirst connection and said second connection, providing one degree ofaxial freedom between said service boat and said vessel by thecombination of said first connection and said second connection, andusing the power of said service boat to position said vessel in adesired location.
 2. The method of claim 1, further comprising saidcombination of said first connection and said second connectionproviding a second degree of axial freedom.
 3. The method of claim 1,further comprising providing flotation material for said link such thatsaid link is positively buoyant.
 4. The method of claim 1 furthercomprising providing sideways thrust on said service boat to provide alateral force on said link and thereby a lateral force on said vessel.5. The method of claim 4 further comprising the combination of saidlateral forces and axial forces from said service boat onto said linkallows said link to exert forces on said vessel in any horizontaldirection.
 6. The method of claim 1 further comprising said firstconnection being a stab engaging a funnel.
 7. The method of claim 6further providing a cylinder to position said stab prior to enteringsaid funnel.
 8. The method of claim 1 further comprising that said firstconnection being magnetically attached to said vessel.
 9. The method ofclaim 1 further comprising said second connection having a portionpermanently affixed to said service boat and a portion removeablyattached to said permanently affixed portion on said service boat. 10.The method of claim 9 further comprising said removeably attachedportion being a funnel.
 11. A method of providing for the dynamicpositioning of a vessel comprising providing a dynamically positionedservice boat, providing a rigid link, providing a first connectionbetween said link and said vessel, said first connection providing 3degrees of rotational freedom and one degree of axial freedom, providinga second connection between said link and said service boat, said secondconnection providing 3 degrees of rotational freedom and 2 degrees ofaxial freedom, and using the power of said service boat to position saidvessel in a desired location.
 12. A method of providing for the dynamicpositioning of a vessel comprising providing a dynamically positionedservice boat, providing a link capable of pushing or pulling, providinga first connection between said link and said vessel, said firstconnection providing 3 degrees of rotational freedom, providing a secondconnection between said link and said service boat, said secondconnection providing three degrees of rotational freedom, providing onedegree of axial freedom between said vessel and said service boat, andusing the power of said service boat to position said vessel in adesired location.
 13. The method of claim 12, further comprising saidsecond connection provides a third degree of angular freedom
 14. Themethod of claim 12 further comprising providing a second degree of axialfreedom between said vessel and said service boat.
 15. The method ofclaim 12 further comprising providing sideways thrust on said serviceboat to provide a lateral force on said link and thereby a lateral forceon said vessel.
 16. The method of claim 15 further comprising thecombination of said lateral forces and axial forces from said serviceboat onto said link allows said link to exert forces on said vessel inany horizontal direction.
 17. The method of claim 12 further comprisingsaid first connection being a stab engaging a funnel.
 18. The method ofclaim 17 further providing a cylinder to position said stab prior toentering said funnel.
 19. The method of claim 12 further comprising thatsaid first connection being magnetically attached to said vessel. 20.The method of claim 12 further comprising said second connection havinga portion permanently affixed to said service boat and a portionremoveably attached to said permanently affixed portion on said serviceboat.
 21. The method of claim 20 further comprising said removeablyattached portion being a funnel.
 22. The method of claim 12, furthercomprising providing flotation material for said link such that saidlink is positively buoyant.